Someone help me out

[Nicola_M]

A gas explosion destroys houses in today's news.

http://www.bbc.co.uk/news/uk-england-manchester-18594635

What is of note are the words:

"A fire service helicopter with listening equipment is at the scene trying to detect if people are trapped in the rubble."

I can't figure that one out. Place a listening device on the noisiest aircraft known to man. Surely all that's going to pick up is the sound of its own engine and the rotors?

[Kaphias]

I can only assume that it works in a manner similar to noise canceling headphones: the drone on the helicopter is reasonably constant, so the software takes that noise out and listens for any outlying noises.

[Kieran]

Or the microphone is directional, like a shotgun.

Or a combination of the two.

[Hampster]

A dome facing away from the helicopter wouldn't capture the sounds, it's only the vibrations that may effect the detection... interesting...

[larjeet]

I would think that infared cameras would be of more use. But I believe they would be using sonar or ultrasound sensors lowered from the helicopter into places that where unsafe for rescuers to reach

[Kieran]

The problem with the infrared camera is that the buildings could still be hot from the explosions.